Table LED Matrix, Weeks of debugging, column problems

[jukeman]

The problem was what he was wanting to do with a simple circuit in the beginning!

Watch the video link and you will see the leds flashing instead of staying on steady, it's just like they are running from a pulse width modualtion setup with a low frequency and you can see them flash.

I guess from the way you talk to me that I don't know what I'm talking about, it works don't it. I just don't like the flashing. They should either be on or off and not flashing! Why does it need to scan the matrix were not running video across it, come on i'm not a newbe here!

[Ioannis]

Hey Kevin, cool down. I am trying to help here.

You may know little, much or everything, I don't argue about that.

I am pointing out some cases that I susspect or have opposed during my experiments and would like someone have pointed me when I was awake all night to spot them...

Anyway, seeing a matrix, one guesses that scanning is needed. I did not quite understood from the beggining that finally only one element should stay on at a time.

The programm in C was writen to scan the matrix. For a completely different application than yours.

For your case, yes, if you want to just light one element at the time, only the col and row that corresponds to must be ON. There is no need for scanning resulting the flickering you see.

So the programm should only set the corresponding bits at proper level (0 or 1) and wait for a few seconds. At C I don't know how though.

Ioannis

[mekohler]

Im concered that the LED clusters are not as bright as when I tested them individually, and they are barely shining through the diffusive glass I have over them.

Kevin suggested to change the program to not run pulses. Is anyone familiar enough with this to help me?

Here are some measurements:

Voltage:

1) From PSU Ground to a single LED Cluster (6 LED's in parallel with a resistor) COLUMN input: 5.25 V

2) From PSU Ground to single LED Cluster (6 LED's in parallel with a resistor) LED Cluster ROW input: 3.85 V

3) From ROW input to COLUMN input of a single cluster: .86V (I dont think this means anything, since this is an incorrect way to measure V)

Current:

4) Removing one LED cluster in the all lit column and connecting column output of LED below and column input of LED above to the meter: 2.53 using 20mA setting/resolution

5) Removing one LED cluster in the all lit row and connecting row ouput of LED to the left and row input of LED to the right to the meter: 12.17 using 20mA setting/resolution

[mekohler]

Update: I still have row 1 and column 1 on for testing. I removed one of the clusters in the first column and tried lowering the resistor values of 300 to 150, 47, and no resistors. The brightness obviously goes up as I go down in R, but even at no resistors the cluster is not as bright as an extra "test" cluster detached from the table and connected to a 9V battery.

I used this extra cluster connected to a 9V battery for my intial table construction, as it was bright enough for the glass, and I assumed it would be getting 12V, so I knew for sure it would be sufficient.

Any ideas?

[nomad]

the plain fact is it is a matrix. in order to control each led without having a separate output for each led it needs to switch from row to row or col to col. in other words scan the matrix. if your seeing hy flash, then it is not scanning fast enough. by adjusting the scan rate and pulse width you can control the brightness. as loannis said it's doing what it's supposed to be doing. with a scope you can actually see the pulses and determine if they are too short or too far apart or anything else that is happening with them. if you just want them all on or off take out the pic and insert a switch.

[nomad]

you will never get the matrix as bright as your test cluster. to switch say 5 rows only one is on at a time. so each row is on only 20 percent of the time max.

[nomad]

i'm not a C programmer but it looks like the line that says 4ms delay is your delay between rows. you could try making 259 a smaller number. i think that would get rid of your flicker but may make it even dimmer.